The present invention relates generally to improvements in video cassette recorders and, more particularly, to an improved circuit for automatically eliminating the recordal of unwanted portions of a television broadcast.
Video cassette recorders (VCR) are currently in widespread use and are operable in a record mode for recording a television broadcast on a suitable video cassette tape. In a playback mode, the VCR is operable for coupling the previously recorded television broadcast to a conventional television receiver where it may be viewed at the convenience of the viewer. The use of VCR's has therefore provided a facility enabling the viewers of television broadcasts to control their viewing habits to an extent not heretofore possible by, for example, recording a television program at the time of its broadcast and then viewing the recorded program at a time convenient to the viewer. In order to provide an additional degree of viewer convenience, it has been proposed to provide apparatus controlling the VCR in its record mode for automatically inhibiting the recordal of unwanted portions of a television broadcast and, in particular, for inhibiting the recordal of advertising commercials which are typically interspersed throughout desired programming materials such as movies, sporting events and the like. Ideally, the advertising commercials are completely eliminated without viewer intervention such that, upon playback of the video cassette tape, only the desired programming material is presented to the viewer.
In one known system of the foregoing type, apparatus is provided for eliminating color commercials when recording a monochrome television program. In particular, the presence of the color burst in the television signal used to transmit the color commercial is detected and places the VCR in a "pause" mode wherein the video tape is not allowed to advance. Since the television signal used to transmit the monochrome program does not include a color burst, this programming material will be recorded in a normal manner. It will be appreciated that apparatus of this sort is severely limited in that it will not function properly for television signals transmitting color programming.
In another known prior art apparatus, means are provided for simultaneously detecting the absence of sound and the fade of video to black level which normally occurs for a short interval at the beginning and end of commercials. In response to the detection of these conditions, the VCR is placed in "pause" for a fixed time interval, usually about 30 seconds. While a device of this type is operable in the case of television programs transmitted in color, it suffers from the disadvantage that 30 seconds of the programming material following the last of a series of commercials will not be recorded due to the fade detection made at the end of the last commercial. Also, if a commercial is longer than 30 seconds the last part of the commercial will be recorded.
In view of the foregoing, it is a basic object of the invention to provide improved apparatus automatically operating a video cassette recorder for inhibiting the recordal of unwanted portions of a television broadcast.
It is a more specific object of the invention to provide an automatic commercial eliminator for use with a video cassette recorder which is useful in association with both monochrome and color programming materials and which minimizes the amount of non-recorded desired programming and also insures that any normal commercial, regardless of its length, will not be recorded.